1. Field of the Invention
The present invention relates to a cleaning device for a vehicle lamp. More particularly, the present invention relates to a technique for downsizing an overall cleaning device in a direction perpendicular to the sliding direction of a piston.
2. Related Art
A vehicle lamp, such as a headlamp, is an important functional part in a vehicle. Therefore, an impairment of a beam illumination capability should be avoided.
One cause of the impairment of the illumination capability of the vehicle lamp such as a headlamp is a staining of a front lens. For example, during traveling on an unpaved road at the time of a rainfall or snow thawing, muddy water splashed by an own vehicle, a preceding vehicle, or an oncoming vehicle may attach onto a front lens. Thereby, a hindrance to the illumination of the beam is occurred by the mud on the front lens. Therefore, it has been necessary to remove stains such as the mud attached to the front lens at an appropriate timing even during traveling.
Accordingly, there is a cleaning device for a vehicle lamp to wash away the stains such as mud attached to the front lens by injecting a cleaning liquid to the front lens, as necessary.
In the cleaning device for a vehicle lamp, since the cleaning liquid is injected to the front lens, the injection port should be located further forwardly of the front lens. However, if the nozzle having the injection port is located further forwardly of the front lens, a projected object is present at a front portion of the vehicle. This is not favorable in terms of safety. Accordingly, JP-A-08-058533 discloses a cleaning device, so-called pop-up type, in which the nozzle having the injection port is normally located on the reverse side of a bumper and the like, and the nozzle is adapted to project forwardly of the front lens when the injection of the cleaning liquid is required.
In the cleaning device disclosed in JP-A-08-058533, a cleaning liquid passage is formed in the piston, the nozzle is connected to its front end portion, and a check valve is provided at its rear end portion. When the device is not in use, i.e., when the injection of the cleaning liquid is not carried out, the piston is held in a state of being retracted inside the cylinder by a spring interposed between the cylinder and the piston. As the cleaning liquid is supplied into the cylinder, the piston starts to project from the cylinder, and when the piston has projected from the cylinder and the pressure of the cleaning liquid within the cylinder has increased to more than a predetermined level, the check valve is opened, and the cleaning liquid flows into the piston is then injected from the injection port of the nozzle.
In the cleaning device for a vehicle lamp disclosed in JP-A-08-058533, the respective members making up a check valve are arranged in the sliding direction of the piston, and the respective members making up the check valve are operated in the sliding direction of the piston to effect the opening and closing of the cleaning liquid passage. For this reason, the size of the check valve in the radial direction of the piston becomes large, and the outside diameters of the piston and the cylinder are bound to be also large. Accordingly, a large space is required in the heightwise direction when the device is installed in the vehicle.
In a vehicle, such as an automobile, there are many cases where a large space cannot be secured in the vertical direction around a headlamp in view of the requirements in design. Hence, there is an increased demand for a cleaning device which can be installed in a small space on the upper or lower side or on the left or right side of the headlamp.